Optimal shakedown design of base isolated structures

摘要

The minimum volume design problem of finite element discretized elastic perfectly plastic structures is studied. Two different resistance limits are considered: the elastic shakedown and the instantaneous collapse, imposing for each a suitable safety factor. The dynamic features of the structure are determined taking also into account an appropriate base isolation system in order to reduce the seismic effects. According with the Italian code the actions are all considered as a combination of fixed loads and quasi static perfect cyclic loads, the latter depending on the dynamic properties of the given structure. Two different formulations of the minimum volume design are proposed: the first one is related to the optimal design of the structure without any base isolation system with constraints on the elastic shakedown behaviour and on the instantaneous collapse, the second one is related to the optimal elastic shakedown design of the isolated structure. The two obtained optimal structures are compared in order to evaluate the effect of the base isolation system.